feat: M3 — 伏笔账本 + 节奏引擎 + 大纲（含并发记账 bugfix）

- 伏笔账本：纯函数状态机(OPEN/PARTIAL/CLOSED/OVERDUE) + ForeshadowLedger repo；验收后到期扫描(BackgroundTask 自建 session 置 OVERDUE)；登记/状态变更端点
- 节奏 + 三审齐：foreshadow-analyst + pace-checker 并入 LangGraph 并行审(REVIEW_SPECS)，collect 分列落 chapter_reviews(conflicts/foreshadow_sug/pace)，review SSE 加 foreshadow/pace 事件
- 大纲：outliner Agent 产 OutlineResult(含 foreshadow_windows)，POST /outline 逐章 upsert outline 表；GET /foreshadow?status= 看板
- 前端：伏笔四泳道看板(OVERDUE 琥珀) + 大纲编辑器(窗口徽标) + 节奏节拍图(▁▃▅) + 审稿页消费 foreshadow/pace SSE
- bugfix(T3.8)：并行三审共用请求 session 记账触发 'Session is already flushing' → foreshadow/pace 静默丢失；SqlAlchemyLedgerSink.record 改 add-only(靠端点/事务 commit)，加并发回归测试
- M3 E2E：真实 DB + mock 网关零 token 走通 埋设→进展→验收后扫描 OVERDUE→看板 + 大纲含窗口 + 三审齐 SSE/留痕；E2E 暴露并钉住上述 bug
- 门禁绿：mypy 111 / pytest 228(0 xfailed) / alembic 无漂移；前端 gen:api/lint/tsc/vitest 69/build

apps/web/lib/outline/outline.ts

@@ -0,0 +1,49 @@
+// 大纲编辑器纯逻辑：按卷分组、伏笔窗口徽标文案、接近回收窗口提示（UX §6.7）。
+// OutlineChapterView/ForeshadowWindowView 已由 OpenAPI 强类型，无需手动收窄。
+
+import type { ForeshadowWindowView, OutlineChapterView } from "@/lib/api/types";
+
+export interface VolumeGroup {
+  volume: number;
+  chapters: OutlineChapterView[];
+}
+
+// 按 volume 分组（保持章号升序）；卷号升序。
+export function groupByVolume(
+  chapters: readonly OutlineChapterView[] | undefined,
+): VolumeGroup[] {
+  const byVolume = new Map<number, OutlineChapterView[]>();
+  for (const ch of chapters ?? []) {
+    const list = byVolume.get(ch.volume) ?? [];
+    byVolume.set(ch.volume, [...list, ch]);
+  }
+  return [...byVolume.entries()]
+    .sort(([a], [b]) => a - b)
+    .map(([volume, list]) => ({
+      volume,
+      chapters: [...list].sort((a, b) => a.no - b.no),
+    }));
+}
+
+// 伏笔窗口徽标文案：`⚑ F-012 (40-60)` / `⚑ F-012 (≤60)` / `⚑ F-012`。
+export function windowBadgeLabel(window: ForeshadowWindowView): string {
+  const from = window.expected_close_from;
+  const to = window.expected_close_to;
+  if (typeof from === "number" && typeof to === "number") {
+    return `⚑ ${window.code} (${from}-${to})`;
+  }
+  if (typeof to === "number") return `⚑ ${window.code} (≤${to})`;
+  if (typeof from === "number") return `⚑ ${window.code} (≥${from})`;
+  return `⚑ ${window.code}`;
+}
+
+// 接近回收：本章号落在窗口 [from,to] 内（提示「本章可回收」，UX §6.7 ⚑ 可回收）。
+export function isCloseWindow(
+  chapter: OutlineChapterView,
+  window: ForeshadowWindowView,
+): boolean {
+  const to = window.expected_close_to;
+  if (typeof to !== "number") return false;
+  const from = window.expected_close_from ?? to;
+  return chapter.no >= from && chapter.no <= to;
+}